|From Keyboard, October 1997 Written by Zon Vern Pyles
Feels like deja vu: I'm completely surrounded by analog synthesizers in my studio, and we're sending spaceships to Mars again. Am I having one of those flashbacks we were promised? No, I'm the lucky one who gets to review the new Encore Electronics 8-channel MIDI-to-control-voltage converter, the Expressionist. Let's grab some patch cords and plug in.
The Expressionist is a 1 U rackmount MIDI-to-CV converter with eight CV output jacks and the same number of gate/S-trigger outputs. It's a MIDI interface for voltage controlled analog synthesizers that converts MIDI data from your controller and/or sequencer into the proper voltages - and voltage types. You can hook up as many as eight mono synths - such as a Sequential Pro-One, Roland , SH-101, Minimoog, ARP 2600, Doepfer A-100, etc. - in any combination to create an 8-channel multitimbral system. The Expressionist will also let you group CV outputs together to turn your rig into an 8-voice polyphonic synth.
The Expressionist includes a DIN sync output for converting MIDI clock, start, stop, and continue messages into the sync pulses required by many pre-MIDI drum machines and digital sequencers. Besides a MIDI in connector, it has a MIDI out that is software-switchable to a MIDI thru. A 1/4" jack allows you to plug in a footswitch to step through the 100 user setups.
The simple front panel features a power switch, a bright 2-line x 20- character backlit LCD, and five buttons for setup editing: increment, decrement, parameter (actually used for cursor control), page forward, and enter. The Expressionist is tedious to program because it doesn't have a data knob. The manual didn't mention it, but I discovered that you can step back a page by holding the page button and touching the decrement button. Until I tried this, I was pushing the page button 18 times to get to a page I had inadvertently passed. In addition, the manual didn't mention the footswitch jack at all. [Ed. Note: Tony Karavidas, designer of the Expressionist, tells us he's soliciting suggestions for footswitch applications. His email address appears in the At A Glance box at left.]
Interfacing synths to the Expressionist requires a variety of cables that depend on the brand of synths you're hooking up. Most Moogs need 1/4"-to-S- trigger cables for triggering the Moog's envelope generators, and standard 1/4"-to-1/4" cables for CV. I felt the manual should have provided some information on how to make the S-trigger cables, since they're an absolute necessity and not readily available from any music store. Luckily, a trip to Radio Shack provided me with the proper 2-pin plug (Cat. No. 274-201A). I soldered it to one end of a 1/4" cable and within minutes had my Minimoog hooked up and MIDIed. Roland, ARP, and Doepfer synths, among others, need 1/4"-to-1/8" cables for CV and gate hookups.
Once you've hooked up your collection of analog synths to the Expressionist, it's time to employ one of its most useful features: built-in tuning offset and tracking for each of its eight CV outputs. Anyone who has ever had to use a teeny screwdriver to tune and scale their analog oscillators will appreciate this. However, I would have preferred it as a global procedure rather than having to define these values per setup. As it is, you must copy a completed setup to each new setup to avoid entering offset and tracking values for each of your synths every time.
[This section in brackets is the caption under the second image]
[No other MIDI-to-CV converter offers as many interface possibilities as the Encore Expressionist. Its back panel is packed with wall-to-wall jacks. There's no room for three MIDI connectors, so the MIDI out can be software-switched to a thru.]
You can select any of the Expressionist's 100 setups using MIDI program changes. Each setup contains 18 pages of parameters including MIDI channels, voltage types, note ranges (which allows keyboard splits), transposition (up to ±36 semitones), pitchbend depth (up to ±12 semitones), and two types of portamento: variable and fixed. Variable portamento means that covering a range of five octaves takes the same amount of time as it does to cover a single step. It's called "variable" because the Expressionist will vary the portamento rate so that the time it takes to reach the second note is the same regardless of the distance between the two notes. With a fixed rate, the glide rate stays the same regardless of distance; in other words, a five-octave glide will take five times as long as a one-octave glide. The portamento rate ranges from 0-99, which is the equivalent of 0-30 seconds. I would have preferred more resolution at the low end of the scale, which is where I consider the portamento effect most useful. The glide in this range was either too fast or too slow for my taste.
The Expressionist's operating system software is upgradeable via MIDI and it uses Flash memory, which means you won't have to take it to a service center in five years to have its backup battery replaced. (It doesn't have one.) Using the Expressionist with modular synthesizers offers some real power. You can choose to use any or all of its eight CV outputs as modulation sources, each with four individually assignable MIDI modulation sources, which include velocity, aftertouch, note position, or any of the first 121 continuous controller numbers. That's 32 simultaneous modulation sources, folks. Gimme some patch cords!
LFOs & Polygroups
The Expressionist has three global LFOs, each with six waveforms to choose from independently: sine, triangle, square, positive and nega tive sawtooth, and random/sample and hold. All are bipolar (positive and negative) except for the square wave, which is positive only, making it easier to tune trills and octave jumps. You can, in other words, assign LFO 1 to CV channel 1 with a sine wave, LF0 2 to CV channel 4 with a positive sawtooth, and LFO 3 to CV channel 5 with a sample-and-hold wave. The LFO rate ranges from 0.125 to 12Hz. LF0 depth is adjustable per CV channel and can be modulated by MIDI controllers, but the rate cannot. However, you can sync the LFOs to MIDI clock using a retrigger parameter that tells the Expressionist how many MIDI clocks (0-99) to receive before it restarts the positive phase of the LFO.
One really nice thing about having LFOs built into the Expressionist became apparent while I was playing my Minimoog via MIDI: I no longer had to use oscillator 3 as an LFO; I could create fat, three-oscillator sounds and still have vibrato and filter sweeps! CV outputs can be grouped together into polygroups to create a polyphonic system. The Expressionist provides two polygroup setups, so if you have enough synths you can build two independent polyphonic synth systems. There are five voice-stealing algorithms:
Rob None - Any notes exceeding the polyphony of your setup won't be heard; sounding notes sustain while they're held.
Rotate - Starting with the first, each CV channel takes turns being stolen.
Reassign - A note played on a channel will steal a note from the same channel.
Rob High - Steals the highest note currently playing.
Rob Low - Not the actor; this one steals the lowest note currently playing.
One feature on the long-out-of-production Roland MPU-101 MIDI-to-CV converter that isn't duplicated by the Expressionist is a rotate mode in which each incoming note triggers a different synth in a rotating manner. For external storage of memory data, the Expressionist allows system- exclusive dumps that's currently in the edit buffer.
Once I got past a couple of front-panel quibbles, the Expressionist worked perfectly. My Minimoog has been transformed into a new instrument and my 2600s have never had such happy expressions on their faces. For those reasons alone, the Expressionist is going to stay right where it is.
What a MIDI-to-CV Converter Does
A MIDI-to-control-voltage converter transforms MIDI messages such as note- ons and -offs into the proper gates and control voltages. A gate is an electrical signal that triggers an analog envelope generator, just as if you were pushing a key on the synth's keyboard.
MIDI note-on = +5V (open the gate). MIDI note-off = OV (close the gate).
Moogs use S-triggers, which stands for "shorting trigger;" here's how those commands are handled:
MIDI note-on = short to ground (close the switch). MIDI note-off = open the switch.
MIDI-to-CV converters also change MIDI note numbers and controllers into varying voltages. Most analog oscillators are of the volt-per-octave persuasion, which means each additional volt of direct current raises the pitch one octave. Moog, ARP, Roland, and Doepfer are just a few of the manufacturers who use this system. Yamaha and Korg chose the Hertz-per- octave method of voltage control, in which octaves are achieved by doubling the voltage. Half-steps, pitchbend, and vibrato are the result of smaller changes in voltage levels on both types.